After talking with Grissom at the slot machines, when Melanie goes to leave, an officer reaches to help her down. But in the next shot from the opposite direction, the officer is not there at all.
Catherine would not be allowed to re-enter a crime scene with an open wound in case she contaminated the evidence.
In the beginning of the episode, as Catherine is talking to the officer at the scene, the dead body blinks.
In the morgue, the actor can be seen breathing.